Infinitely variable friction drive



May 19, 1959 J. E. KOPP 2,385,986

v INFINITELY VARIABLE FRICTION DRIVE Filed April 18, 1957 ESheets-Sheet1 Fig.1 9 6 15 May 19, 1959 J. E. KOPP 2,886,986

INFINITELY VARIABLE FRICTION DRIVE Filed April 18, 1957 2 Sheets-Sheet 2United States Patent 2,886,986 INFINITELY VARIABLE FRICTION DRIVE JeanErnst Kopp, Berne, Switzerland Application April 18, 1957, Serial No.653,691

Claims priority, application Switzerland July 7, 1956 10 Claims. (Cl.74-796) The present invention relates to infinitely variable frictiondrives of the type having friction rolls with doubleconical surfaces andwith an axis of rotation extending at an angle to the common axis of therunning surfaces, between which the friction rolls are arranged, whereinthe transmission ratio between the driving and the driven shaft may beinfinitely varied by moving the friction rolls in the direction of theaxis of the running surfaces.

In such friction drives hitherto known the conical surface lines of thefriction rolls, contacting the running surfaces, are parallel to theaxis of the running surfaces and these two surfaces are located in acommon plane. Owing to the contact pressure, in the supportingarrangement of the friction rolls very high bearing pressures willarise, which tend to increase. the frictional losses of the drive and todecrease the efiiciency of same.

It is an object of the invention to avoid the above disadvantage and toprovide an infinitely variable friction drive, in which the conicalcircumferential surfaces of the friction rolls, engaging the runningsurfaces, are'inclined to the axis of the running surfaces and the tworunning surfaces are staggered to each other in the direction of theircommon axis so that the bearing pressures of the friction rolls producedby the contact pressure are compensating each other at least partly. Asit has been found, the efliciency of the drive can thereby besubstantially increased. i

l The present invention will now be described more fully with referenceto the accompanying drawings illustrating, byway of example, severalembodiments of the invention, and in which: i

Fig. 1 is a section through a friction drive according to .the inventionhaving double-conical friction rolls with inclined axes;

--Fig. 1a is a section showing the axial and radial components of :thecontact pressure applied to a friction roll;

Fig. 2 shows the same friction drive as illustrated in Fig. 1, but inthis case the friction rolls occupy a position for anincreasetransmission ratio;

Fig. 3 is a' construction in which the outer ring remains stationarywhile the friction rolls revolve together with their associated carriersin a planetary manner;

Fig. 4, is a construction in which simultaneously two groups of frictionrolls according to Fig. 3 are arranged in parallel relationship;

Fig. 5 is a modification, wherein two groups of friction rolls arearranged in series connection; one of said groups is formed in principleaccording to Fig. 1 while the second group is built fundamentallyaccording to Fig. 3, and Fig. 6 is an embodiment having frictionrollswhich are supported on their circumferential area.

Referring to the example shown in Fig. 1, the numeral 1 designates ahousing having a cover 2 threadedly secured therewith. A shaft 3 isrotatably supported in the housing 1 by means of a ball bearing 18, anda shaft 4 is supported in the cover 2 bymeans of ball bearings 19. Anumber of friction rolls 7, for instance four, which are provided withdouble-conical surfaces arearranged 2,886,986 Patented May 19, 1959 on acarrier 6 in planetary relationship and rotatably supported so thattheir rotary axes 8 are disposed at an angle to the axis of the shafts 3and 4. The axes 8 either may form part of the rolling bodies 7, or maybe inserted into said bodies. The axes 8 together with the frictionrolls 7 can be moved in the direction of their longitudinal axis.

The friction rolls 7 are in frictional engagement on one side with arunning surface of a disk 10 and on the opposite side with the runningsurface of a ring member 9. The disk 10 and also the ring member 9 arerotatably supported on the shafts 4 or 3, respectively, but they are notdirectly secured therewith in rigid manner. The ring 12 which is rigidlyconnected to the shaft. 4 forms a coupling together with the disk 10,-since these parts are provided with annular end surfaces facing eachother,

wherein are formed oppositely inclined sloping surfaces.

Cooperating with these sloping surfaces are balls 11 which are spacedapart from each other by means of a ball cage. This coupling providedbetween disk 10 and shaft 4 acts as a device for automaticallycontrolling the contact pressure exerted by the disk 10 upon thefriction rolls 7, as the balls 11 climb up on the inclined surfaces andurge the disk 10 against the friction rolls 7. The conicalcircumferential surface of the friction rolls 7, which engages therunning surface of the disk 10, is inwardly inclined so that anincreased contact pressure will be obtained on the engaged surface bymeans of the axial movement of the disk 10. The conical circumferentialsurface of the friction rolls 7 contacting the running surface of thering member 9 is also arranged at an incline, preferably of the samesize, so that these two surfaces are parallel to each other. The conicalcircumferential surfaces contacting the running surfaces are inclinedwith respect to the axis of rotation of the running surfaces in such amanner, and the two running surfaces are staggered in the direction oftheir axis or axially spaced apart from each other so that thedextrorotatory momentum, exerted upon the friction rolls 7 in theillustrated plane of Fig. 1a and produced by the axial component P ofthe contact pressure together with the distance b, corresponds at leastapproximately to the laevorotatory momentum which is produced by theradial component Q of the contact presits running surface, respectively,will be adjustable in radial direction.

Arranged between the ring member 9 and the ring 13 which is rigidlyconnected with the shaft 3 are balls 11 cooperating in similar mannerwith inclined surfaces, in order to obtain a device for the automaticcontrol of the contact pressure. By the arrangement of such a device onthe input shaft and also on the output shaft, the automatic regulationof the contact pressure is obtained within the entire regulating range.

The carrier 6, which within the cover 2 is supported on the shaft 3non-rotatably but axially movable, comprises a toothed section formed asa rack in which a toothed gear 16 engages. The carrier 6 may bedisplaced in axial direction by rotating the gear 16.

In the position shown in Fig. 1, the disk 10. engages the friction rolls7 at a large diameter, the member 9 on the p other hand makes contact ata small diameter; thereby a on a small diameter, while thernemberBcontactsxm In Fig. 2 the carrier 6 is shown moved in axial direction sofar that the disk 10 contacts the friction rolls 7 a large diameter;thereby a step-up ratio is transmitted to the shaft 3 by the shaft 4.Infinitely variable transmission ratios may thus be adjusted by movingthe carrier 6 in axial direction.

The spring 17 exerts an axial pressure upon the ring 12 and the disk 10so as to provide a friction pressure hetween the disk 10, the ring 9 andthe friction rolls during starting before the contacting device becomeseffective.

In Fig. 3 the shaft 4 is supported in the cover 21, threadedly securedto the housing 20, by of the ball bearings 19 and has mounted on it thedisk 16*, balls 11 and ring 12 of the contacting device in the samemanner as shown in Fig. 1. The friction rolls '7- are journalled in acarrier 22, which is rotatably supported with one end upon a bearingbushing 2ftv of the cover 21 and with the other .endin a socket25 bymeans of a ball bearing 24. I116 socket: 25 is splined tothe housing 2d,but movable axial-direction and is provided with a toothed r aek section26 which is engaged by the gear wheel 27 whieh in turn may be rotated bya handwheel located at the outside. The ball bearing transmits thedisplacing movement of the socket 25 to the rotary carrier 22. The ringmember 28, which is frictionally engaged by the friction rolls 7, is inthis case movably arranged within the housing 20. This ring member formsa contacting device together with a ring 29 rigidly secured to thehousmg 20 and with balls 30 which cooperate with inclined surfacesprovided on the end faces of the rings 28, 29. The balls climb up on thesloping surfaces, as soon as load is applied, and force the ring member28 tight against the friction rolls 7. The friction roll carrier 22 isconnected with the shaft 31 by a spline connection under the influenceof a spring. Upon rotation of the shaft 4, the friction rolls 7 arerotated by frictional engagement, in which operation said rolls inplanetary manner roll upon the running surface of the ring member 28.The carrier 22 is thereby set in rotary motion and drives the shaft 31.In the same manner as previously explained with reference to ,Fig. 1, achange in the transmission ratio is effected by displacing the carrier22 in axial direction, in which case the contact radii extending betweenthe friction rolls 7 and the running surfaces of the ring member 28 onthe one hand and the disk 10 on the other hand are changed.

In the embodiment of the invention according to Fig. 4, two groups offriction rolls 7 are arranged on a carrier 32, which is rotatablysupported in a similar manner as shown in Fig. 3 and is axially movableby means ofan adjusting device 26, 27. The friction rolls 7 arranged inthe described planetary manner roll, as in Fig. 3, around two ringmembers 28 arranged within the housing 33, each of said members 28 beingassociated with a contacting device 29, 30. Moreover, a disk 10cooperates with each group of friction rolls. Both disks 1.0 arearranged on a shaft 34 together with their associated contacting devices11, 12. The transmitted power can be increased due to the parallelarrangement of the two groups of friction rolls. Any number of groupscould be disposed in place of the two groups of friction rolls employedin the example shown.

The construction according to Fig. also shows two groups of frictionrolls 7. The right hand group corresponds in principle to the groupshown in Fig. 1, while the left hand group is similar to the oneillustrated in Fig. 3, wherein if the shaft 35 represents the inputshaft.

the take-off part 36 of the first group .is rotatably connected with thedriving part 37 of the second group by means: of a contacting device 38.The part-37 is supported in an intermediate wall 40 of the housing 41 byauballbearing 39. The remaining construction of these two-groups isexactly similar to the constructions according to Figs. 1 and 3. Theshaft 42 represents the takeoff shaft. A separate adjusting device 15,16 and 26, 27, respectively, is provided for each step of the frictiondrive. This-design serves toenlarge the adjustable range and at the sametime to increase the starting torque. The first step according to Fig. 1delivers a high ratio of trans mission, while great torques may beobtained by the second step according to Fig. 3. By this combination ofthe two groups, high ratios of transmission and simultaneously largetorques can thus be obtained, when at the driving side first theconstruction according to Fig. 1 is chosen.

Fig. 6 shows a modification having cylindrical friction rolls 43, thecircumferential area of which is supported in an axially movable carrier45 by means of roller bearings 44 so that the axis of rotation of thefriction rolls 43 is inclined with respect to the common axis'of therunning surfaces. of the disk 47 rigidly mounted on the shaft 46 and ofthe ring member 48. The end faces of the friction rolls 43 are formed asconical surfaces 49, 50 in such a manner that the conical surface 49includes an angle more acute than the conical surface 50. Upon axialdisplacement of the carrier .45, the. distanceis thereby changed betweenthe running surface of the disk 47and the running" surface .oftheringmember 48. For this reason the latter is arranged axially movable inthe housing 51 and is urged'against the friction rolls 43 by springs 52.In the position shown, the distance between the parts 47 and.48 becomesgreater when the rotary axis of the friction rolls 43 will be placed incloser proximity to the running surface of the ring member 48. In thisposition the rotational speed of the friction rolls 43 will be lower,when the .disk 47 is the driving member, and the springs 52 will be morecompressed the closer the friction roll axis approaches the ring 48.Thereby the contact pressure exerted upon the friction rolls 43 becomesgreater according to the lower speed and the greater output torques. Bya corresponding formation of the inclined surfaces of the friction rollsand of the springs 52, the contact pressure can automatically beregulated so that the transmitted torque at each time corresponds to theadjusted speed, whereby it is possible to obtain a constant power outputat various initial speeds without the necessity of providing acontacting device such as shown in Fig. 1 and without the occurrenceofan excess of contactpressure at higher initial speeds. This kind ofcontrol of the contact pressure may also be applied for friction rollsaccording to Fig. 1 by forming. the conical surfaces in a correspondingasymmetrical manner. The contact pressure could also be regulated sothat it increases with increasing initial speeds, in order to transmitgreat power outputs at high speeds,byproviding for instancein Fig. 6theinner conical surface 50 of the friction rolls 43. with a moreacute-angledjformation than the outer conical surface 49. Assumingithedisk 47 to be the driving member, then the contact pressure would begreater if the disk 47 would' be moved closer to the axis of thefriction rolls.

Bycorrespondinglyforming the described conical surfaces, the contactpressure of the friction rolls may be adjusted to any torquecharacteristic.for both constructions according to the invention, theone showing a s'ta tionary carrier accordingto Fig. 1 and also the otherprovided with a revolving carrier according to Flg. 3'.

Instead of arranging the springs 52 between the'ring' member 48 and thehousing 51, said ring member'48 supported along the circumferencethereof the friction.

rolls could also be supported by means of a central shaft in a mannershown forinstance in. Fig. 1.

-In place of the illustrated adjustment. by. the intermediary of thegear'wheel16 and-"the toothedraek't 1S (Fig. 1), any otherkind ofadjustmentcould be em ployed, such as a lever enabling directly'orindirectly the adjustment of the carrier from the outside.

The proportion of the 'akial'pressure exerted upon the drive shaftsandconsequently upon the ball bearings which have to withstand thispressure may be regulated at will by the selection of the angle ofinclination between the disk (Fig. l) and the contact area of thefriction rolls 7, or between friction rolls 7 and ring member 9,respectively. The more obtuse this angle is with respect to the rotaryaxis 3 and 4, respectively, the smaller will be the proportion'of theaxial pressure on the total contact pressure. v I Y.

.The power flow in the friction drive can take place in both directions,that means it is possible to use -e.g. in Fig.1 not only th e shaft 4but also the shaft 3 as driving shaft.

In similarmanner as in Figs..,l and-2 the .running surface of the disk10 is adjustable in radial direction due to the support of said disk onthe'shaft 4 pr'ovisio'n o'f clearance, both running surfaces or" elsethe support of the friction rolls could be adjustable in radialdirection.

"The advantages of an infinitely variable friction drive according. tothe invention are:

Only'two friction surfaces act upon the friction rolls.

The friction rolls are mounted between the friction surfaces so thatonly little axial pressure is produced and exerted upon the driving ordriven shaft, which pressure may be reduced to the value zero of thetotal contact pressure. The efliciency of the friction drive therebywill be high and the construction simple. The bearing pressures exertedupon the friction roll axles by the contact forces may be partly orwholly nullified, resulting into an additional increase in etficiency.

Any number of friction rolls around the periphery of the contact zonecan be arranged, which rolls together transmit the power.

In a simple manner various groups of friction rolls can be connectedtogether in order to obtain increased power or an increased range ofregulation, or both.

The construction is simple and of compact design.

I claim:

1. An infinitely variable friction drive comprising means definingrunning surfaces having a common axis, friction rolls between saidrunning surfaces and rotating about an axis of rotation inclined to saidcommon axis of the running surfaces, a driving shaft and a driven shaftoperatively associated with the running surfaces, means affording aninfinite variation of the transmission ratio between said driving andsaid driven shaft by displacement of the friction rolls in the directionof said common axis of the running surfaces, said friction rolls beingprovided with double-conical circumferential surfaces contacting therunning surfaces, the generatrices of the conical surfaces of thefriction rolls contacting the running surfaces being inclined at anangle to the common axis of said running surfaces, the two runningsurfaces being urgeable against the friction rolls and being staggeredwith respect to each other in the direction of their common axis by anamount remaining constant during the adjustment of the friction rolls,so that the bearing pressures of the friction rolls produced by thecontact pressure compensate each other at least partially.

2. An infinitely variable friction drive comprising a driving shaft anda driven shaft, running surfaces arranged along a common axis androtatable on the shafts,

friction rolls arranged between said running surfaces and havingdouble-conical circumferential surfaces contacting same, said frictionrolls being arranged to rotate about an axis inclined to said commonaxis of the running surfaces, means for displacing the friction rolls inthe direction of said common axis of the running surfaces in order toinfinitely vary thetransmission ratiobe'tw een the driving and thedriven shaft, pressure means associated with each running surface andadapted, upon rotation of the shafts to exert an axial pressure upon therunning surface urging them against the friction rolls, thedouble-conical surfaces of the friction rolls being inclined withrespect to the said common axis of the running surfaces and the latterbeing staggered with respect to each other so that the bearing pressuresof the friction rolls resulting from the contact pressure compensateeach other at least partially.

3. An infinitely variable friction drive comprising means defining,running surfaces having a common axis, friction rolls between saidrunning surfaces and rotatingabout an axis of rotation inclined to saidcommon axis 'of the running surfaces, a driving shaft and a driven shaftoperatively associated with the running surfaces, means affordinganinfinite variation of the. transmission ratio between said drivingandsaid driven shaft by displacement ofthe friction rolls in thedirection of said common axis ofthe running surfaces, said frictionrolls being provided with double-conical circumferentialsurfacescontacting the running surfaces, the generatrices of the conicalsurfaces of the friction rolls contacting the running surfaces beinginclined at an angle to the common axis of said running surfaces, thetwo running surfaces being urgeable against the friction rolls and beingstaggered with respect to each other in the direction ofv their commonaxis by an amount remaining constant during the adjustment of thefriction rolls so that the bearing pressures of the friction rollsproduced by the contact pressure compensate each other at leastpartially, the friction rolls and the running surfaces being parallel toeach other in at least two groups so that the transmission ratio of allgroups together corresponds to the ratio of one group, the transmittedpower of all groups together increasing in the same ratio as the numberof groups, only one common adjusting device being provided for the axialadjustment of all groups of friction ro Is.

4. An infinitely variable friction drive according to claim 3, in whichat least two groups of friction rolls are arranged on a common carrierupon which the: adjusting device acts.

5. An infinitely variable friction drive comprising running surfaceshaving a common axis, friction rolls, arranged between said runningsurfaces and rotating about an axis of rotation inclined to said commonaxis of the running surfaces, a driving shaft and a driven shaftoperatively associated with the running surfaces, means affording aninfinite variation of the transmission ratio between said driving andsaid driven shaft by displacement of the friction rolls in the directionof said common axis of the running surfaces, said friction rolls beingprovided with double-conical circumferential surfaces contacting therunning surfaces, the inclination of said doubleconical surfaces withrespect to the common axis of the running surfaces being such and thelatter being staggered with respect to each other in direction of theircommon axis so that the bearing pressures of the friction rolls producedby the contact pressure compensate each other at least partially, and arotatable carrier for the friction rolls, one of the running surfacesbeing fixed against rotation so that the friction rolls roll around thefixed running surface in a planetary manner.

6. An infinitely variable friction drive according to claim 5, in whichthe friction rolls and running surfaces are arranged on behind the otherin a plurality of groups Isvuchdthat the transmission ratios of thegroups are com 7. An infinitely variable friction drive as claimed inclaim 6, wherein in one group the carrier of the friction rolls isnon-rotatable and the two running surfaces are rotatably arranged, whilein another group the carrier of the friction rolls is rotatable and oneof the running surfaces is disposed in. non-rotatable and the other inrotatable manner.

8. An infinitely variable friction drive comprising running surfaceshaving a common axis, friction rolls, arranged between said runningsurfaces and rotating about an axisof rotation inclined to said commonaxis 'of the running surfaces, a driving shaft and a driven shaftoperatively associated with the running surfaces, means a'ffording aninfinite variation of the transmission ratio between said driving andsaid driven shaft by displacement of the friction rolls in the directionof said common axis ofthe running surfaces, sai'd friction rollsbeingprovided with double-conical circumferential surfaces contacting.the running surfaces, the inclination of said double conic'alsurfaces'with respect to the common axis of the running surfaces beingsuch and the latter'b'e'ing staggered with respect to each other indirection of their common axis so that the bearing pressures of thefriction r'o'lls' produced bythe contact pressure compensate each otherat least partially, the two conical surfaces of the friction rolls beingformed asymmetrically by providing one conical surface with a more acuteangle than the other surface.

9. An infinitely variable friction drive according to clairnl8, whereinone of the running surface carrier-mem hers is axially movable againstspring pressure so that the contact pressure is automatically adjustedto the desired torque characteristic upon axial movement of the frictionrolls.

10. An infinitely variable friction drive comprisingmeans definingrunning surfaces having-a common axis,

friction rolls between said running surfaces androt'atin'g about an axisof rotation inclined to said common axis of the running surfaces; adriving "shaft and a driven shaft operatively associated with therunning surfaces, means References Cit'edin the: file of'thistpatent'UNITED STATES PATENTS 2,574,530 Castagna Nov. 13,1951 FOREIGN PATENTS683,063 Germany Oct. 30, 1939 148,001 Sweden D60 7, 1954 182,150Switzerland Jan. 31, 1936

